Process of making electrical resistance units



c. WIBT. PROCESS OF MAKING ELECTRICAL RESISTANCE UNITS.

APPLICATION FILED OCT. 22, I918.

Patented May 4, 1920.

CHARLES WIRT, F PHILADELPHIA, P NNSYLVANIA.

PnocEss OF MAKING ELECTRIC L EEsIsTANC UNITS.

Specification of Letters Patent.

Patented May 4, 1920.

.Application filed October 22, 1918. Serial No. 259,167.

To all whom it may concern Be it known that I, CHARLES VIRT, a citizen of the United States, and a resident of the city and county of Philadelphia and State of Pennsylvania, have invented a certain new and useful Process -of Making Electrical Resistance Units, of which the following is a specification.

My invention relates to resistance units and has for its object toiprovide 'aprocess for the production ofadevice which will be convenient in form, not liable to injury in use, having high insulating qualities, of

high resistance in proportion to its size,

give a wide range of variation, which will be cheap and simple of construction, having sufficient mechanical strength to render it safe and durable, and by means of which such a device may be cheaply and expeditiously manufactured.

These and further objects will more fully appear in the following specification and accompanying drawings considered together or separately.

I have illustrated one embodiment of my invention in the accompanying drawings in which like parts are designated by similar characters of reference, and in which Figure 1 is perspective View of the metallic shell of the unit.

Fig. 2 is a similar view of the resistance element before it is embedded in the shell.

Fig. 3 is a longitudinal sectional view of the completed unit, the section being taken on the line 3-3 of Fig. 1.

Fig. 1 is a transverse section on the line 4-4 of Fig. 3.

Fig. 5 is a plan view of the apparatus employed in carrying out one step in the process of making the unit.

Fig. 6 is a section on the line 6-6 of Fig. 5, and Fig. -7 is a transverse section showing a modification.

In carrying out the embodiment of the invention illustrated I employ a conductor 1 of any approved form and of any desired cross section. I prefer however to make it of wire of small cross sectional area. Preferably the wire is of iron because of its high temperature variation, i. e., the resistance of the wireincreases with the temperature.

The wire is wound, in the form of a helix, on a core 2 of electrical insulating and heat resisting material. I have found that so-called lava is admirably adapted for this purpose, but other suitable materials may be employed. Each end of the wire 1 is in electrical contact with a conducting element 3 which latter are secured by means of screws 4:, or otherwise, to the core 2 at or near opposite ends thereof.

Each element 3 comprises a member 4; which is in contact with the core 2 and conductor 1, a standard 5 extending at a right angle to the core, and a foot 6 which extends in the direction longitudinally of the core but on a different level. Each foot is provided with a slot 7 and a perforation 8. I have shown the core 2 as of rectangular cross section but it will be understood that it may be made of other shape.

The core with the conductor 1 and the elements 3 attached thereto is inclosed in a trough-shaped casing 9 of metal or other suitable material. The casing comprises a top-member 10- and two side members 11, 11.

The longitudinal edges of the side members are flanged as at 12 and the flanges are preferably bent inward toward the top member as shown.

The flanges 12 are of such a width that the space between them will not permit of the entrance or removal of the core. The core must be placed in the casing'or shell through one of the open ends thereof.

The relative dimensions of the casing 9 and core 2 are such that between the boundaries of the casing and the core there will be a considerable space and this space is filled with an insulating material 13 of such a character that it may be made up in more or less fluid form and poured into the space between the core and casing and which will harden on drying. The shell is filled with the material 13 flush with the open side and ends of the case and the flanges 12 will be embedded in the filling and will retain the same in place. The standards 5 of the elements 3 project through the filling and through the open side of the casing as shown.

In operation the unit is secured in place to a suitable base by means 'of screws or bolts which are engaged in the slots 7 of the feet 6 and may be attached in-the line by the said screws or bolts, or by binding-posts secured in the perforations 8.

In the practice of my invention the apparatus illustrated may be employed. The apparatus contemplates a frame comprising a bottom 14, end walls 15, side walls 16 and a central partition 17 extending from one end wall to the other and equidistant from and parallel to the side walls.

' In carrying out the process a plurality of casings 9 is placed within the spaces formed by the partition and the walls 15 and 16 with.

the top member 10 of each casing resting on the bottom 14 of the frame. Before the casings are placed in the frame a core with its conductor 1 and elements 3 in position thereon is placed inside of each shell.

The feet 6 of each element 3 rest one upon a side wall 16 and one upon the partition 17 and are retained in proper position by means of pins or bolts 18 carried by the frameclosed by the vertical members thereof.

The casings are assembled in the frame side-by-side and in contact one with the other and the channels from one end wall to the other are completely filled with the shells with the cores in position.

The insulating material 13 in semi-fluid formis now poured into the shells through the open sides thereof filling each shell level with the edges of the open side and embedding the core 2, conductor 1 anda portion of each element 3. The frame or tray is then given a shaking 'or jigging motion whereby air bubbles are worked out and the material settled down. The shells are left in the tray until the material sets after which they are removed and the material hardened as by drying. The unit thus formed is then given a coat of paint or other covering and is ready for use.

The operation of the device and the carrylng out of the process are obvious from the above description.

In accordance with the provisions of the patent statutes, I have described the principle of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but Idesire to have it understood that the apparatus shown is merely illustrative and that the invention may be carried out in other ways. Having now described my invention what I claim and desire to secure by Letters Patent is 1. The process of making resistance units, which comprises winding a conductor of high electrical resistance upon a core, securing an element to each end of the core and of the conductor, supporting the core within a shell having open ends and an open side by means of the elements in such a manner that the core, conductor and elements will be out of contact with the shell, temporarily open side by means of the elements in such a manner that the core, conductor and elements will be out of contact with the shell, the shell having a portion projecting inwardly, temporarily closing the ends of the shell, filling the shell through the open side thereof to .the level of the edges thereof with' an insulating heat resisting material in liquid or semi-liquid form.

3. The process of making resistance units, which comprises winding a conductor of high electrical resistance upon a core, se-

curing an element to each of the core and of the conductor, supporting the core within a shell having open ends and an open side by means of the elements in such a manner that the core, conductor and elements will be out of contact with the shell, the shell having an integral portion projecting inwardly, temporarily closing the ends of the shell, filling the shell through the open side thereof to. the level of the edges thereof with an insulating heat resisting material in liquid or semi-liquid form.

4:. The process of making resistance units which comprises winding a conductor of high electrical resistance upon a core, securing an element to each end of the core and of the conductor, supporting the core within a shell having open ends and an open side by means of the elements in such a manner that the core, conductor and elements will be out of contact with the shell, the shell having an integral portion projecting diagonally into the space inclosed by the shell, temporarily closing the ends of the'shell, filling the shell through the open side thereof to the level of the edges thereof with an insulating heat resisting material in liquid or semi-liquid form.

5. The process of making resistance units which comprises winding a conductor of high electrical resistance upon a core, securing an element to each end of the core and of the conductor, supporting the core within a shell having top and side members, the ends and one side of the shell being open, the free edges of the side members being flanged diagonally into the space inclosedby the shell, the core being supported by the elements in such amanner that the core, conductor and elements will be out of contact with the shell, temporarily closing the ends of the shell, filling the shell through the open 8 side thereof to the level of the edges thereof With an insulating heat resisting material inili uid or semi-liquid form.

6; he process of making resistance units,

Within a shell having open ends and an open side by means of the elements in such a manner that the core, conductor and elements will be out of contact with the shell, temporarily closing the ends of the shell, filling the cell through the open side thereof to the level of the edges thereof With .an insulating heat resisting material in liquid or semi-liquid form, jigging the shell to Work out air bubbles and settle the mate-- rial, and drying the material.

g The process of mal r i ng resistance units, which comprises Windmg a conductor of securing anelement to each end of the core,

attaching each end of the conductor to an 7 element, placing the core and attachments Within a shell having an open side and tWo open ends and in such a manner that the elements 'Will project through the open side, placing a plurality of'shells within a tra with the open sides of the shelves upwar the shelves resting side-by-side in contact with each other and filling the tray, the sides of the tray closing the open ends of the shells and rising above the level of the shells, securing the elements to the Walls of the tray whereby the core and conductor of each shell Will be suspended in the shell but out of contact With the 'shell and tray, filling the shells through the open sides to the level of the edges thereof With a heat resisting insulating material in liquid or semi-liquid form and embedding the core, conductor and a portion of each element therein, jigging the tray to expel air bubbles from the material, drying the material andremoving the units from the tray.

This specification signed and witnessed this eighteenth day of October, 1918.

' CHARLES WIRT.

Witnesses:

A. E. BENTON, J NO. ROBT. TAYLOR. 

